This invention relates to the field of semiconductor test systems, and more particularly to the field of device-under-test (DUT) board configuration interconnection.
Semiconductor test systems are used for testing integrated circuit (IC) devices to verify their performance characteristics. In a typical test system, the IC device is placed in a test fixture that is mounted on a device-under-test (DUT) board.
Semiconductor test systems are increasingly required to bring large numbers of high integrity digital and analog signals to bear on ever smaller and more dense device input and output pin arrangements. Such testers have drivers and receivers physically concentrated in the vicinity of a test head equipped with a DUT board. However, to interface with a variety of semiconductor devices, a means must be provided for switching between the fixed signal locations of the tester and the variable configurations of device pinouts. Reconfiguring this tester-to-device interface while attaining ever higher electrical performance is a major challenge for the engineers that design these testers.
While early semiconductor test systems were largely confined to testing either memories or digital logic or simple analog integrated circuits, current generations of testers frequently include the capability to do "mixed signal" testing. These mixed signal testers test integrated circuits that have digital and analog circuitry mixed together at a high level of density. Analog signal testing places an extra burden on the tester-to-DUT interface. As an additional burden on the tester-to-DUT interface, the analog frequencies and digital data rates involved keep moving higher and higher.
Low level analog signals that must be measured accurately and very high frequencies and data rates require a tester and tester-to-DUT interface with a very high level of signal fidelity, a very low level of noise, and a minimum of cross-talk.
One approach to meeting this need is to design dedicated DUT boards for each device type, but this is an approach that is both expensive and time consuming, putting an unacceptably long delay due to the required design cycle in the way of adequately testing a new device type. And, in the field of mixed analog and digital integrated circuits, each device type tends to have a different pin-out arrangement.
Using discrete jumper wires, either single conductor or coaxial cables, to reconfigure the tester-to-DUT interface is inconvenient and does not produce the required levels of signal integrity. Moreover, with high density inputs and outputs, numerous jumper wires, especially coaxial ones, eventually take up too much room and become harder to connect and disconnect. And, in the more complicated world of mixed signal testers, there are more types of circuitry residing on the DUT board. With more types of circuitry present, the average distance to the right type of circuitry for a particular pin on the device increases, further complicating the task of using discrete jumper wires to reconfigure the tester-to-DUT interface.
What is desired is an easily reconfigurable DUT board interconnection means that is electrically and mechanically reliable, that has low noise and cross-talk, and that permits high density mixed digital and analog devices to be tested.